Chapter 9 - Alkynes

Dihalides + NaNH2 or warm KOH are reagents used for

Elimination reactions

H2 + Lindlar’s catalyst, Na or NH3, and HX are reagents used for

Addition reactions

H2O, H2SO4, HgSO4 and BH3 + H2O2 are reagents used for

Hydration reactions

Cold KMnO4 and O3 + H2O are reagents used for

Oxidation reactions

Both types of elimination reactions form

Alkyne 

H2 + Lindlar’s catalyst form

Cis alkenes

Na or NH3 forms

Trans alkenes

HX forms

Vinyl hallides

X2 forms

Vinyl dihalides

H2O, H2SO4, or HgSO4 and BH3, H2O2, and NaOH are used for

Hydration reactions

H2O, H2SO4, or HgSO4 are reagents that form

Ketones via enol intermediate!

BH3 + H2O2 are reagents that form (HINT! Different between internal and terminal alkynes!)

Aldehydes if terminal, ketones if internal

DILUTE KMnO4 or O3 + H2O are reagents used for

Oxidation reactions

Dilute KMnO4 forms

Diketones

Ozonolysis (O3) forms

Carboxylic acids

How does the structure change in elimination reactions?

Single bonds > triple bonds. No halogens.

How does the structure change when using H2+Lindlar’s catalyst OR Na/NH3 in addition reactions?

Alkyne > alkene. Cis = Lindlar’s. Trans = Na/NH3.

How does the structure change when using H2 + Pt/Pd/Ni?

Alkyne > alkane

How does the structure change when using HX?

Alkyne > geminal dihalide. Halogens on the originally triple bonded carbons.

How does the structure change when using H2SO4/HgSO4?

Alkyne > enol > ketone. The C=O group ends on more substituted carbon.

How does the structure change When using BH3/H2O2?

Alkyne > enol > aldehyde (terminal) OR ketone (internal). The C=O group ends on less substituted carbon.

How does the structure change when using warm KMnO4/O3 in oxidation reactions?

Alkyne > carboxylic acid. Splits the chain at the triple bond into 2 acids. Terminal alkynes produce 1 carboxylic acid + CO2.

Warm KMnO4 forms

2 carboxylic acids

Which alkyne reactions have anti-addition?

Na/NH3, Halogens (X2),, Halohydrins